1. Field of the Invention
The present invention relates to a vibration gyro sensor and a method for producing the same. In particular, the present invention relates to a vibration gyro sensor for detecting the angular velocity of rotation by utilizing the Coriolis force generated when a ring member (vibrator) vibrated with a driving piezoelectric/electrostrictive element is rotated while being vibrated.
2. Description of the Related Art
The gyro sensor which is a sensor for detecting the angular velocity of rotation, has been hitherto used, for example, for inertial navigation systems of aircraft and shipping. Recently, the gyro sensor is used for vehicle-carried navigation systems and for attitude control systems of automatically guided robot vehicles. Further, the gyro sensor is also used, for example, for picture blurring-preventive systems of VTR cameras. In such circumstances, a compact type gyro sensor is required, which is appropriately used in various fields as described above. Accordingly, the vibration gyro sensor has attracted attention.
As well-known, the vibration gyro sensor of this type has a basic structure comprising a driving piezoelectric element and a detecting piezoelectric element which adhere to a vibrator formed of a constant resilience metal represented by an elinvar alloy. In a rectangular coordinate system of X, Y, Z axes, when the vibrator is rotated about the z axis while giving bending vibration in the x axis direction to the vibrator by using the driving piezoelectric element, the Coriolis force acts in the y axis direction to the vibrator. Accordingly, a strain or distortion is generated in the detecting piezoelectric element in accordance with bending vibration in the y axis direction caused in the vibrator by the Coriolis force. The strain is detected as a voltage (or as an electric charge). The angular velocity is determined on the basis of the detected voltage.
However, in the case of the conventional vibration gyro sensor as described above, the amount of displacement of the vibrator, which is based on the vibration induced by the driving piezoelectric element, is small. Therefore, the voltage (electromotive force), which is detected by the detecting piezoelectric element, is small. As a result, the conventional vibration gyro sensor involves a problem that the sensitivity is low.
In addition, the driving piezoelectric element and the detecting piezoelectric element are glued and fixed to the vibrator by using an adhesive. Therefore, the adhesive intervenes between the vibrator and the piezoelectric elements. As a result, the stress is absorbed by the adhesive. Due to this fact, together with other factors, if any, a problem arises in that the detection sensitivity is lowered.
When the vibrator comprises a member which is composed of a sound chip or a tuning fork formed of an elinvar alloy, a problem arises in that the characteristics of the vibrator tend to be affected by an ambient magnetic field, because the elinvar alloy is a ferromagnetic material. Further, due to the shape or the material of the vibrator as described above, there is an implicit problem that it is difficult to perform processing or machining when the resonance frequency of the vibrator is adjusted.